Domains from services like Mailinator are banned from many websites for the reasons stated above. Mailinator provides alternate domains which work around this ban in many cases.
Another problem for users is that mail sent to Mailinator often disappears for unknown reasons. Before using Mailinator a user should first send it some test e-mails to determine the system's reliability for themselves.
Mailinator strips many headers from incoming e-mail. This means that users wanting to verify the e-mail sender or server may be unable to do so. And according to their FAQ "Plain text is best, html is filtered. Images, attachments, and fancy stuff are simply stripped away." Unfortunately this often results in incomplete or garbled messages.
The "Domains from services like Mailinator..." paragraph is accurate. Some sites do ban it but so far no sites I know of have kept up with our alternate domains (see our home page) for a recent list. I'm still baffled why websites send-away customers but I guess that's their business. If I'm not sure I'm going to want or use some webservice, I test the waters with mailinator address. If they don't let me, I usually then just don't bother testing it. I'm sure other folks then resolve to give them their real address, or go waste 5 minutes signing up for a fake yahoo address, but for me its rarely worth it.
The next paragraph describes that emails "disappear for unknown reasons". Um, I thought I was pretty clear in the FAQ about how Mailinator handles email. Emails live for a few hours - not a day, not 1 hour - a few. It's completely dependant on how much email its getting at the time. (As a data point, I notice right now emails are sticking around 183 minutes).
Although I fully agree with the latter part, if you want to test mailinator out - please do !!! Send anything you like :)
Finally the last paragraph states that we remove some headers. This is nuts. The code has never removed any headers whatsoever. And on every page showing an email, there is a "text-view" link where you can see the email PRECISELY as mailinator received it. Headers, dirty words, mime-encoded images, you name it. In other words, that paragraph is dead wrong.
I haven't seen any garbled emails for a long time either (probably was when the parsing code was originally written). We support most encodings, (japanese and russian emails look cool), I suppose if you send an email with some odd encoding that Java doesn't support or mis-specify an encoding things might look garbled. Regardless - if you see a garbled email - please let me know!
I tried to replace the last paragraph with one explaining that the "text-view" sort of proves its not true, but my change was undone immediately (so fast I'd guess it was automated) because it was "Wikipedia Vandalism". I'm not too fond of the paragraph that says emails "disappear" given that its pretty misleading, but God forbid I try to fix that one.
If you're a common Wikipedia poster - please feel free to fix this entry. All I'm hoping to get up there is (something closer to) the truth.